Smudge resistant transfer sheet and process of making same



y 1951 M. J. HOLIK 2,554,909

SMUDGE RESISTANT TRANSFER SHEET AND PROCESS OF MAKING SAME Filed April 15, 1946 Patented May 29, 1951 SMUDGE RESISTANT TRANSFER SHEET AND PROCESS OF MAKING SAME Melville J. Holik, Berwyn, Ill., assignor to Ditto, Incorporated, Chicago, 111., a corporation of West Virginia Application April 15, 1946, Serial No. 662,401

14 Claims. 1

The invention relates to transfer sheets and more particularly to dye-carrying impression type transfer sheets such as the so-called hectograph and spirit process carbon paper and typewriter ribbon which have a base sheet coated with a water and alcohol soluble aniline dye-containing composition which is transferable to a contacting surface by the application. of pressure or impact such as may be produced by a pencil or the keys of a typewriter.

There has always existed the undesirable characteristic of smudging on the fingers and hands of an operator using hectograph or spirit process dye composition carbon papers. This characteristic of smudging has always seemed concomitant with the nature of the formulation.

In order for a good transfer of dye composition to be effected from the carbon sheet backing to the master paper, the dye particles must not adhere too tenaciously to the backing and must break away freely and cleanly to conform to the configuration of the character being duplicated. Thus, it is necessary to maintain thi trait.

Previously, attempts at coating a film over the dye-containing transfer coating to prevent smudging have resulted in poor let-down, or difficulty in maintaining flexibility or non-aging properties. Attempts at changing the vehicle for the dye or the dye itself have resulted in an in-' ferior type of carbon paper which even then did not have adequate protection from smudging.

An object of this invention is to overcome the above mentioned disadvantages and produce an improved smudge-proof impression type transfer sheet which is capable'of forming a clear and otherwise satisfactory dye-containing impression on a master or other copy sheet.

Other objects and advantages of this invention will become apparent as the following detailed description progresses, reference also being made to the accompanying drawing.

The drawing represents a cross-section of a transfer sheet made in accordance with this disclosure, showing in diagrammatic and enlarged form the base sheet I of paper, tissue, fabric or the like, having a pressure transferable coating of a solid wax-oily material 2 containing water soluble basic aniline dye particles 3, and a'surface layer of water insoluble dye base particles 4.

In accordance with this invention, I react the dye on the surface of the dye-containing transfer composition of the transfer sheet with a basic substance adapted to convert the dye to its water insoluble color base, and which also by itself or in conjunction with a reducing agent will reduce the color base to the even more insoluble and colorless leuco base.

Suitable reagents for this purpose include ammania and polyamines containing at least two nitrogens each having at least one hydrogen attached to a. nitrogen. The preferred materials are polyamines containing at least 1 NH2 group and at least 1 NH group in the molecule. These materials react with the dye on the surface of the transfer sheet without hindering the letdown or transfer or copying qualities. This results in a surface layer of an insolubilized colorless compound. This layer of compound is not soluble in the perspiration of the fingers and hands, nor in moisture which may be present. The surface of the transfer sheet may thus be touched and rubbed Without imparting dye to the skin. No impairment of the properties of the transfer sheet is effected.

Typical examples of suitable polyamines are ethylene diamine, propylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, phenylene diamine, hydrazine, primary alkyl hydrazine, and unsymmetrical hydrazines. Ammonia in its anhydrous conditions is suitable as it has an active hydrogen and it behaves similarly to the polyamines having 2 NH groups in the molecule, but it is not as effective as the polyamines, particularly the polyamines having NH2 groups, and it is much more difiicult to satisfactorily apply to the surface of the carbon paper as it must be applied in gaseous form, or with some solvent which does not hydrolyze the ammonia.

The polyamines may be applied to the surface of the dye-containing composition on the transfer sheet in various ways. For example, the liquid polyamines may be sprayed on the surface. The liquid or solid polyamines dissolved in solvent may likewise be applied by spraying or brushing on the surface. The polyamines may be dissolved in any type of solvent, including water and alcohol.

In another embodiment of this invention, I use an amine or other basic substance capable of reacting with the dye to remove the acid and which may or may not have reducing properties such as to convert the insoluble color base to the leuco base (as is the case for the polyamines having at least 2 NH2 groups in the molecule) in conjunction with a reducing agent which is capable of bringing out reduction. Suitable reducing agents include hydroquinone, hydroxy sulphonic acid structures of bisulphite products or carbonyl compounds and sodium formaldehyde sulfoxylate (salt of sulfinio acid). The reducing property of hydroquinone is greatly enhanced in alkaline solution so that such a material used in conjunction with the polyamines is particularly effective.

Ammonia and the polyamines are operable for the purpose of this invention with all types of water and ethyl alcohol soluble basic aniline dyes. Dyes of this type which are often used in hectograph and spirit process transfer sheets are crystal violet, methyl violet, magenta, brilliant green, chrysoidine, safranin, rhodamine and Bismarck brown.

The following example is used to illustrate this invention:

A hectograph or spirit process carbon paper having a transfer coating consisting of parts by weight carnauba wax, 30 parts by weight mineral oil, 10 parts by weight parafiin wax and 50 parts by weight of crystal violet, is sprayed on its transfer surface with ethylene diamine. The ethylene diamine reacts with the dye on the surface, converting the dye to the color base by neutralization of the acid used to form the salt (which is the colored dye). Thus the dye reverts from the hydrochloride of hexamethylpararosaniline to the water insoluble color base hexamethylpararosaniline. This reaction is extremely effective to safeguard against smudging since the color base is much less soluble in water than the salt.

The ethylene diamine rather slowly reacts with the color base to produce the leuco base by reduction, and this material also is effective against smudging since it is colorless and even more water insoluble than the color base. Preferably, however, the reduction is abetted by using with the ethylene diamine or after the application of ethylene diamine some stronger reducing agent such as hydroquinone or the sulphonic sulfite complex. In the presence of the alkaline media afforded by the basicity of the diamino compounds, the reduction proceeds quickly to the leuco base. The quinoid grouping in the crystal violet structure is destroyed, and the reversion occurs to the trityl carbinol.

The reactions which take place are believed to be as follows, although it is to be understood that the invention is not limited to the theory as to what takes place as expressed by these reactions:

Due to the availabliity of two amino groups, a

hydrate may be formed with one amino group,

leaving the other group free, as:

H N-R-NH pluswater yields 6H[l E3-RNH conceivably, then, the free amino group reacts with the dye to remove the acid, and the hydrated portion of the molecule can complete the conversion to the color base. The reaction:

CH3 CH3 CH 3 amino Crystal violet CH3 CH3 5 F N-O-Q-ON NH-.-R-Ni1. 1

H. ta 3111.

Color base ifll] Further reduction CH CH CE; Ha Cs g CH3 Lcuco base The amount of amine and the time of application to the dye-containing transfer composition is, of course, regulated so that not all of the dye salt is converted to the color base or the leuco base. Ordinarily a layer not more than 2% of the total thickness is converted to the colorless dye bases. This thin layer is sufiicient to prevent smudging and yet it is not sufficient to materially affect the copying qualities of the transferred dye composition.

One important advantage of my method is that it allows the formation of an extremely thin protective layer, such as one or two molecules of dye base in thickness. Such thin layers can not be practically produced by methods involving the coating of film-forming protective coatings over the colored dye composition.

In addition to converting a thin layer of the dye on the surface of the transfer sheet, I may also apply over the insolubilized dye layer. a solution of some film former such as zein, casein, or hydroxy cellulose ether, particularly the aluminum salt. I may also incorporate such filmforming material in the polyamine solution. This additional precaution is particularly useful for protection against excessive handling as with the ends of typewriter ribbons in the threading operation, or the edges of carbon paper.

While I have described certain preferred embodiments of my invention, many modifications thereof may be made without departing from the spirit of the invention; and I do not wish to be limited to the detailed examples, formulas and proportions of ingredients herein set forth, but desire to avail myself of all changes within the scope of the appended claims.

I claim:

1. A transfer sheet comprising a base sheet having a coating containing a basic aniline dye and having a surface layer over said dye containing coating containing -a water insoluble base of said dye.

2. A transfer sheet comprising a base sheet having a coating of a pressure transferable composition containing a basic aniline dye and having a surface layer over said dye containing coating containing a water insoluble base of said dye, and substantially free from said basic aniline dye.

3. A transfer sheet comprising a base sheet having a coating of a pressure transferable wax composition containing a basic aniline dye and having a surface layer over said dye containing coating of a, wax composition containing a water insoluble base of said dye.

l. A smudge resistant transfer sheet comprising a base sheet having a pressure transferable coating of a wax composition having dispersed therein particles of a water soluble basic aniline dye, and having a surface layer over said dye containing coating in which said wax composition contains a water insoluble base of said dye and is substantially free from said basic dye.

5. A smudge resistant transfer sheet comprising a base sheet having a pressure transferable coating of a wax composition having dispersed therein particles of a water soluble basic aniline dye, and having a surface layer over said dye containing coating in which said wax composition contains the water insoluble color base of said dye and is substantially free from said basic dye.

6. A smudge resistant transfer sheet comprising a base sheet having a pressure transferable coating of a wax composition having dispersed therein particles of a water soluble basic aniline dye, and having a surface layer over said dye containing coating in which said wax composition contains the leuco base of said dye and is substantially free from said basic dye.

'7. The process of making a smudge resistant transfer sheet which comprises contacting the surface of a basic aniline dye containing transfer layer of a transfer sheet with a reducing and a basic agent from the group consisting of anhydrous ammonia and polyamines having at least one hydrogen attached to each of at least two nitrogens, said basic agent and reducing agent being adapted to react with said aniline dye to convert said dye to a water insoluble colorless base, and for a period of time sufiicient to give a layer of water insoluble colorless base not more than 2% of the thickness of said total transfer layer.

8. The process of making a smudge resistant transfer sheet which comprises contacting the surface of a basic aniline dye containing transfer layer of a transfer sheet with a polyamine having at least one hydrogen attached to each of at least two nitrogens, said polyamine adapted to react with said aniline dye to convert said dye to a water insoluble base, and for a period of time suflicient to give a layer of water insoluble colorless base not more than 2% of the thickness of said total transfer layer.

9. The process of making a smudge resistant transfer sheet which comprises contacting the surface of a basic aniline dye containing transfer layer of a transfer sheet with a polyamine having at least one hydrogen attached to each of at least two nitrogens, and a reducing agent, said polyamine and reducing agent being adapted to react with said aniline dye to convert said dye to a water insoluble colorless base, and for a period of time sufficient to give a layer of water insoluble colorless base not more than 2% of the thickness of said total transfer layer.

10. The process of making a smudge resistant transfer sheet which comprises contacting the surface of a baslc aniline dye containing transfer layer of a transfer sheet with ammonia under substantially anhydrous conditions to convert said dye to a water insoluble base, and for a period of time sufficient to give a layer of water insoluble base not more than 2% of the thickness of said total transfer layer.

11. The process of making a smudge resistant transfer sheet which comprises contacting the surface of a basic aniline dye containing transfer layer of a transfer sheet with a polyamine adapted to react with said aniline dye to convert said dye to a water insoluble base, said polyamine having at least two nitrogens each connected to at least one hydrogen, and for a period of time sufficient to give a layer of water insoluble colorless base not more than 2% of the thickness of said total transfer layer.

12. The process of making a smudge resistant transfer sheet which comprises contacting the surface of a basic aniline dye containing transfer layer of a transfer sheet with a polyamine adapted to react with said aniline dye to convert said dye to a water insoluble base, said polyamine having at least two NI-Iz groups, and for a period of time sufficient to give a layer of water insoluble colorless base not more than 2% of the thickness of said total transfer layer.

13. The process of making a smudge resistant transfer sheet which comprises contacting the surface of a basic aniline dye containing transfer layer of a transfer sheet with a polyamine having at least two NHz groups and adapted to react with said aniline dye to convert said dye to a water insoluble base, and a reducing agent, and for a period of time suflicient to give a layer of water insoluble colorless base not more than 2% of the thickness of said total transfer layer.

14. The process of making a smudge resistant transfer sheet which comprises contacting the surface of a basic aniline dye containing transfer layer of a transfer sheet with a polyamine adapted to react with said aniline dye to convert said dye to a water insoluble base, said polyamine having at least two NH2 groups, and hydroquinone, and for a period of time sufilcient to give a layer of water insoluble colorless base not more than 2% of the thickness of said total transfer layer.

MELVILLE J. HOLIK.

No references cited. 

